Up to the present time, effective monitoring and follow-up of user related conditions or parameters such as different physiological parameters, health status, drug compliance has been limited to user's wearing implantable pacemakers and implantable cardioverters-defibrillators (ICDs). Current devices allow access to multiple critical data points reflecting device functionality and overall clinical condition of the user. The most recent advancements in device follow-up has provided for easier access to device stored data by utilizing wireless connectivity and internet based access to data as complement to information derived in point of care settings.
Nevertheless, despite these improvements in technology, there is a need of an improved system for effective monitoring and follow-up of user related conditions or parameters such as different physiological parameters including hydration, glucose levels etc., health status, drug compliance, in connection with organ transplantations to monitor the vitality of organs during transportation from donor to recipient, and to monitor signs or rejection, infections or ischemia, monitor the ovarian cycle using e.g. temperature, and monitoring glucose and hydration to identify alertness of aviators, truck drivers etc. There is clearly a need of such a system that can be used with implantable sensors that are small, reliable, easy and cheap to produce and that can be carried over extended periods of time without any need for re-charge or change of battery. Obviously, implantable pacemakers and implantable cardioverters-defibrillators (ICDs) are not suitable for such a system.
In addition, it would be very beneficial to include an implantable sensor in such improved system. Implantable sensors are sensors configured to be implanted within living tissue, e.g. within a living patient. The patient may comprise an animal or a human. Such implantable sensors are typically used to monitor one or more physiological parameters associated with the patient. For example, an implantable sensor may monitor a patient's blood or other body fluids for the presence or absence of a specific substance. Other implantable sensors may monitor the patient's body temperature. In general, implantable sensors may be used to provide valuable data that assists in diagnosing or treating an illness, or to help maintain or sustain a given level of physiological, chemical, or other activity or inactivity.
An area of high importance in which an implantable sensor and a monitoring system would be of great use is glucose monitoring or diabetes monitoring. At the present time, patients with diabetes rely on monitoring of blood glucose using an invasive blood glucose meter several times every day. Often this method involves drawing a small sample of blood, which is then tested directly for glucose level. There are numerous drawbacks to this method, for example, the patient have to draw samples of blood every day, several times a day at regular intervals, and there is some discomfort associated with drawing blood samples repeatedly. In addition, there is a margin of error, for example, the patient may forget to take a blood sample.
Present glucose sensors, which are typically used with some type of insulin-delivery system in order to treat diabetics, provide data needed to maintain the concentration of glucose within the patient at an acceptable level. Such glucose sensors must perform properly; otherwise, false data may be provided. Such false data (if acted upon) could result in the administration of an inappropriate amount of insulin, leading to death or serious injury. There is thus a critical need in the art for a sensor which is reliable and which can be monitored for proper function on a regular basis. Likewise, there is a need for a glucose sensor which must work properly within certain specific limits of accuracy.
Many implantable sensors require a power source, such as a battery, to power the sensor and transmitter and are therefore useful for only a limited period of time after implantation. After the on-board power source is depleted, an invasive operation, in addition to the initial implantation, will have to be made, if the device is to be removed or replaced.
Hence, there is also a need for an implantable device that can sense or detect one or more physiologic parameter values, and that can be remotely accessed by, for example, a hand held reader to obtain sensed parameters values in a non-invasive manner. No on-board power sources should be used so that the device will never need to be removed from an implantation site in order to replace an electrical power source, and can therefore remain implanted for an indefinite period of time.
In “Wireless Glucose Monitoring Watch enabled by an Implantable Self-sustaining Glucose sensor system” by Rai P. and Varadan V., Progress in Biomedical Optica and Imaging, Proceedings of SPIE8548, 2012, a system including an implantable glucose sensor that can be powered with inductive coupling is described. The sensor can communicate with a watch and glucose data can be displayed on the watch. The sensor described in this article has however only a limited working life since it consumes itself during use.
In Gupta et al, US2007276201, a system for monitoring strain as an indicator of biological conditions, such as spinal fusion, glucose levels, spinal loading, and heart rate is disclosed. The system includes an inter-digitated capacitance sensor, and RF transmitter, and an associated antenna, all of which are microminiature or microscopic in size and can be implanted in a biological host such as a human or animal. An inductively coupled power supply is also employed to avoid the need for implantation of chemical batteries. Power is provided to the sensor and transmitter, and data is transmitted from the sensor, when an external receiving device, such as a handheld RF ID type receiver, is placed proximate the location of the implanted sensor, transmitter and inductively coupled power supply. The implanted sensor, transmitter and inductively coupled power supply can be left in place permanently or removed when desired.
In Yang et al, US2004180391, in vivo or in vitro monitoring of chemical and biochemical species (e.g., pH, or glucose levels) in the interstitial fluid of patients or in a sample of a fluid to be analyzed is provided by a probe (10, 70, 210, 270). For in vivo monitoring, the probe is readily inserted by a minimally invasive method. Optical or electrochemical sensing methods are employed to detect a physical or chemical change, such as pH, color, electrical potential, electric current, or the like, which is indicative of the concentration of the species or chemical property to be detected. Visual observation by the patient may be sufficient to monitor certain biochemicals (e.g., glucose) with this approach. A CAP membrane allows high enzyme loadings, and thus enables use of microminiature probes, and/or diagnosis of low levels of the analyte(s), with sufficient signal-to-noise ratio and low background current.
In “A hydrogel-based implantable micromachined transponder for wireless glucose measurement” by Lei M. et al., Diabetes technology & Therapeutics, Vol. 8, No. 1, 2006, a hydrogel-based implantable wireless glucose sensor is described. The basic structure is a passive micromachined resonator coupled to a stimuli-sensitive hydrogel, which is confined between a stiff nanoporous membrane and a thin glass diaphragm.
In “Die Impedanzmessung zur Beurteilung von Ischämieschäden der humanen Leber in der Vorbereitung zur Transplantation”, Gersing E., Langenbecks Arch Chir (1993) 378: 233-238, “Impedance spectroscopy on living tissue for determination of the state of organs”, Gersing E., Bioelectrochemistry and Bioenergetics (1998) 45: 145-149, “Quantitative analysis of impedance spectra of organs during ischemia”, Gheorghiu M, Gersing E, Gheorghiu E, Annals of the New York Academy of Sciences (1999) 873: 65-71, and “Messung der elektrischen lmpedanz von Organen—Apparative Ausrustung fur Forschung and klinische Anwendung”, Gersing E., Biomedizinische Technik (1991) 36: 6-11, impedance measurements in organ were studied.
To conclude, despite numerous attempts within the art, there is still a need of an improved system for effective monitoring and follow-up of user related conditions or parameters such as different physiological parameters including hydration, glucose levels etc., health status, drug compliance, in connection with organ transplantations to monitor the vitality of organs during transportation from donor to recipient, and to monitor signs of rejection, infections or ischemia, monitor the ovarian cycle using e.g. temperature, and monitoring glucose and hydration to identify alertness of aviators, truck drivers etc. Furthermore, there is still a need for an improved implantable sensor that is small, reliable, easy and cheap to produce and that can be carried over extended periods of time without need for re-charge or change of battery.